A rectifying circuit is proposed in which a unipolar FET (Field Effect Transistor) as a normally-on element and a diode are cascode-connected. The switching speed of the rectifying circuit depends on the diode, and the element withstand voltage capacity depends on the FET.
When the rectifying circuit as stated above is used in, for example, a flywheel diode of a switching power supply operating at a high speed, a delay can occur in turning on due to a parasitic capacity between the gate and the source of the FET.